xdg-shell: Add set_margin request
This is used to figure out the size of "invisible" decorations, which we'll
use to better know the visible extents of the surface, which we can use for
constraining, titlebars, and more.
diff --git a/shared/cairo-util.h b/shared/cairo-util.h
index 7bcbc29..4493b0d 100644
--- a/shared/cairo-util.h
+++ b/shared/cairo-util.h
@@ -165,6 +165,9 @@
frame_opaque_rect(struct frame *frame, int32_t *x, int32_t *y,
int32_t *width, int32_t *height);
+int
+frame_get_shadow_margin(struct frame *frame);
+
uint32_t
frame_status(struct frame *frame);